A multilayer coating with optimized properties for corrosion protection of Al

Abstract

In the context of a universal search for alternatives to chromate-based coatings, which are toxic for both human beings and the environment, a multilayer coating for Al protection purposes is developed and investigated in the current work. The first layer is selected to be a hexamethyldisiloxane-based plasma polymer film (PPF), deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD), due to a number of interesting features that are characteristic of plasma polymers. The second layer is synthesized via the polymerization of the 2-ethylhexyl acrylate monomer initiated from the free radicals trapped on the surface of the PPF during its growth. A subsequent layer of a copolymer of 2-ethylhexyl acrylate and glycidyl methacrylate, poly(EHA-co-GMA), is deposited by spin coating to increase the corrosion resistance of the coating. An improvement in the anti-corrosion properties of the multilayer coating by approximately three orders of magnitude as compared to the uncoated Al substrate is observed. Further enhancement of the adhesion and scratch resistance properties is addressed via UVcrosslinking and the incorporation of in situ generated silica nanoparticles into the final layer.

Study of the synthesis of C:H coating by PECVD for protecting Mg‐based nano‐objects

“…[24] Moreover, on the Bode phase diagrams, the behavior at low and medium frequencies after 7 days of immersion corresponds to a capacitive behavior that can be associated with the capacitance of the alumina layer. [25,26] As it can be seen in Figure 4, when a 200 nm thick C:H layer (P RF = 20 W) is grown on the Al substrate, a significant improvement in the corrosion properties is observed. Namely, the low-frequency modulus (100 mHz) is increased by one order of magnitude (as compared with the uncoated Al substrate) to reach values around 10 7 Ω•cm 2 after 7 days of immersion.…”

“…[ 24 ] Moreover, on the Bode phase diagrams, the behavior at low and medium frequencies after 7 days of immersion corresponds to a capacitive behavior that can be associated with the capacitance of the alumina layer. [ 25,26 ]…”

Synergetic enhancement in the reactivity and stability of surface-oxide-free fine Al particles covered with a polytetrafluoroethylene nanolayer

“…The selected-area electric diffraction (SAED) pattern of the PTFE layer indicates a polycrystalline structure composed of many nano-sized PTFE chains. In general, organic polymers show high permeability to oxygen and water molecules due to their chain structure compared to an inorganic Al 2 O 3 layer 35 . An increase in the thickness of the coating layer considering the permeability of moisture or oxygen is considered to be an effective means of achieving stability matching that of passivated Al 2 O 3 film thinner than 5 nm.…”

Bifunctional coatings: coupling an organic adhesion promoter with an anticorrosion inorganic layer

“…9 Alternatives have to be developed quickly. [10][11][12][13][14][15] To that end, sulfuric anodization could be a suitable option as it brings satisfying results for corrosive protection when the oxide layer is properly sealed. 16,17 Indeed, the oxide layer grown during the anodization process is porous (even columnar on pure aluminum substrates) [18][19][20] and a sealing step is generally performed, for instance using hot water and forming boehmite 3,21 (aluminum oxide hydroxide AlOOH), to provide better protection.…”